Microbial interactions for phenanthrene degradation in soil: Dominant and keystone taxa

The degradation of polycyclic aromatic hydrocarbons (PAHs), such as phenanthrene (PHE), in soil involves intricate interactions within microbial communities, posing challenges in understanding the mechanisms governing these interactions. In this study, metagenomic analyses were conducted in PHE-contaminated soil to address this knowledge gap. The objective was to elucidate microbial interactions between dominant and keystone taxa and their impact on PHE degradation, involving amendments with biochar (BB), functional bacteria (Pseudomonas putida) (Ps), and biochar inoculated with functional bacteria (Pseudomonas putida) (BP). Molecular ecological network analysis revealed microbial degradation cascades orchestrated by indigenous dominant taxa possessing PHE-degrading genes. The dominant taxa played key roles in PHE degradation, with genera positively correlated with nitrate (NO3- -N) content and negatively with ammonium (NH4+-N) content driving anaerobic phenanthrene degradation via nitrate as the preferred electron acceptor, while taxa negatively correlated with PHE degradation were primarily involved in dissimilatory nitrate reduction to ammonium (DNRA). Correlation networks analysis highlighted a unique composition of keystone genera across diverse treatment groups, indicating their sensitivity to soil properties in varying contexts and underscoring their context-dependent roles in influencing PHE degradation. Importantly, positive correlations between dominant and keystone taxa actively involved in PHE degradation were observed. These findings underscore the intricate complexity of microbial interactions in PHE bioremediation, highlighting the ecological significance of keystone genera in the bioremediation of PHE-polluted soil.